This invention relates to thermometers. More particularly it relates to thermometers that display core body temperature from measurements taken at the surface of the human body, such as at the ear.
Body temperature is universally accepted as an important indicator of the physical condition of humans and other warm blooded animals. For many years, the most common method of measuring body temperature was to insert a mercury thermometer into the patient's mouth or rectum. However, conventional mercury thermometers suffer from a number of disadvantages. They are made of glass and are susceptible to breakage. If the glass is broken while the thermometer is in use, the resulting glass debris may cut the patient. The released mercury, if ingested or carried into the bloodstream, can be toxic. In addition, traditional thermometers will not register body temperature until after they are left in the patient's mouth or rectum for several minutes, thus making the measurement slow and uncomfortable.
Advances have been made in thermometers to avoid the fragility and potential toxicity posed by glass and mercury. Examples of thermometers using electronic components are shown in the Cooke U.S. Pat. No. 5,018,875, issued May 28, 1991; the Serperant U.S. Pat. No. 5,056,048, issued Oct. 8, 1991; and the Germanton et al. U.S. Pat. No. 4,536,851, issued Aug. 20, 1985. Use of this technology to measure body temperature results in an electronic version of the traditional glass thermometers; still having to be inserted into the oral or anal cavity. Moreover, this first generation of electronic thermometers continued to suffer from the disadvantages of requiring one to two minutes or longer to register a body temperature.
More recently, instrumentation has been developed to measure human body temperature by remote (i.e., non-contact) reading of the infrared (IR) radiation emissions of the tympanic membrane and the ear canal. This technology is the subject of many patents, including the O'Hara et al. U.S. Pat. No. 4,790, 324, issued Dec. 13, 1988; and the Fraden U.S. Pat. No. 5,178,464, issued Jan. 12, 1993. The IR reading technology also is used in a consumer product marketed by Thermoscan Inc., a San Diego, Calif. company.
The determination of body temperature from an IR read of the ear drum or ear canal avoids the need to insert a probe into the mouth or anus and allows a measurement of body temperature within a few seconds. However, the IR technology is expensive, costing ten times or more than earlier electronic thermometers, and is vulnerable to deterioration of some components as a result of repeated use. For example, the Thermoscan device has an expected life of only 3000 readings before needing replacement.
It is an object of the present invention to provide an electronic thermometer that can register a core body temperature of a mammal without being inserted in the mouth or anus, but without complicated and expensive IR measuring components.
It is another object of the present invention to provide an electronic thermometer that can register a core body temperature of a mammal within seconds of contacting the patient, but without complicated and expensive IR measuring components.
It is still another object of the present invention to provide a thermometer that register a core body temperature within seconds of contacting a patient, but without complicated and expressive IR measuring components.
It is another object of the present invention to provide a thermometer that determines core body temperature with a relatively high degree of accuracy after only a few seconds of contact with the patient.
It is still a further object of the present invention to provide electronic thermometer that is able to register a core body temperature based on a rate of increase in electrical resistance of a sensor in contact with the skin of the patient.
It is yet another object of the present invention to provide an electronic thermometer that registers a core body temperature within seconds of contact of the patient's skin and is able to accurately repeat that determination while continuing to be in contact with the patient's skin.
Further and additional objects are apparent from the following discussion of the present invention and the preferred embodiment.